This invention relates to a medical monitoring system utilizing a remote monitoring unit and, more particularly, to the provision of a communication link for the remote monitoring unit with wider coverage than previously available.
Advances in sensor technology, electronics, and communications have made it possible for physiological characteristics of patients to be monitored even when the patients are ambulatory and not in continuous, direct contact with a hospital monitoring system. For example, U.S. Pat. No. 5,959,529 describes a monitoring system in which the patient carries a remote monitoring unit with associated physiological sensors. The remote monitoring unit conducts a continuous monitoring of one or more physiological characteristics of the patient according to the medical problem of the patient, such as the heartbeat and its waveform.
An important objective of such portable monitoring systems is to establish contact with a central unit, which is in turn in contact with medical personnel and medical records. The ability to establish contact allows the central unit to determine the existence of a medical emergency with the patient, and to render medical assistance to the patient during such an emergency. The ability to establish contact is also important psychologically to the patient, so that the patient knows that (s)he is not alone and out of touch.
At the present time, the portable monitoring systems may establish communication links to the central unit through telephone land-lines, when the patient is in a location where land-line telephone access is readily available, or through the cellular telephone system when land-line access is not available or an emergency suddenly occurs. However, the present inventors have recognized that the existing medical monitoring systems are hampered by the fact that cellular telephone communication links are not available in many parts of the United States and in other countries. This unavailability arises because the cellular system infrastructure is not in place in relatively remote areas and because cellular telephone signals will not penetrate into many structures even if they are within the range of cellular telephone transceiver cell sites. The result is that the remote monitoring unit is unable to communicate with the central unit from many locations. The patient is therefore unable to obtain emergency assistance in those locations, and consequently feels isolated.
There is a need for an improved approach to ensuring wide-area communication availability for remote monitoring units of medical monitoring systems. The present invention fulfills this need, and further provides related advantages.
The present invention provides a medical monitoring system having a remote monitoring unit that has full communications coverage throughout the United States and much of the world. This communications coverage includes a wide geographical area and also locations such as the interiors of buildings that are sometimes unavailable for cellular telephone coverage. This full communications coverage allows the remote monitoring unit to communicate with the central unit under emergency conditions. Equally importantly, the patient being monitored has the peace of mind of knowing that (s)he is never completely out of touch with medical assistance. The present approach may be implemented relatively inexpensively, as the system infrastructure is in place and operating, and it may be adapted to new communications technologies that become available. The necessary addition to the remote monitoring unit adds very little in size, weight, and power consumption to the remote monitoring unit.
In accordance with the invention, a medical monitoring system comprises a sensor system including a sensor associated with a patient, and a remote monitoring unit. The remote monitoring unit comprises a microprocessor in communication with the sensor system, and a portable-monitoring-unit transceiver system in communication with the microprocessor. The portable-monitoring-unit transceiver system includes at least one transceiver selected from the group consisting of a land-line telephone transceiver and a primary wireless-network transceiver such as a cellular telephone transceiver, and preferably both. The portable-monitoring-unit transceiver system further comprises a third-network transceiver, such as a paging-network transceiver. Preferably, the portable-monitoring unit transceiver system includes a land-line telephone transceiver, a cellular telephone transceiver, and a paging-network transceiver.
The medical monitoring system also typically includes a central unit comprising a central unit transceiver which supports communication with the portable-monitoring-unit transceiver system.
The third network is preferably the paging system, but it may be of other types such as a marine network, an emergency network, or the like. The paging system, as it is used today in other applications, is intended to communicate relatively limited amounts of information, typically a brief message to a user that prompts the user to make some further contact or a short reply from the user. In a typical case, the user is prompted to go to a telephone to contact the person who has made the page. Stated alternatively, the paging network has a relatively low bandwidth. Within this constraint, however, the bidirectional paging network has the important advantage that it operates through orbiting communication satellites or an antenna system that give it very wide area coverage and at frequencies that permit its signal to penetrate to locations and to be used in locations that do not permit cellular communication. The paging network has the additional advantage that its infrastructure is in place and operating.
The present inventors have recognized that the use of the paging network for emergency medical monitor communications does not permit the transmission of as high a data rate as does cellular or land-line communication. However, in an emergency where high-bandwidth communication is not available, more limited communication between the patient and the central unit is better than no communication between the patient and the central unit.
Accordingly, in this architecture the microprocessor of the remote monitoring unit usually includes a first processing routine that transmits a full data set over the land line or cellular system when a communication link over one of these transceivers is available, and a second processing routine that transmits a reduced data set over the paging-network (or other third-network) transceiver when a communication link over other transceivers is not available. For example, the first processing routine transmits full physiological information such as a complete heartbeat waveform in the case of heart patients, while the second processing routine might transmit a reduced data set such as heart rate, waveform classification, and other computed information locally derived from the heartbeat waveform by calculations made in the remote monitoring unit. Alternatively, the remote monitoring unit may make multiple transmissions over the paging network, but even in this case it is unlikely that full physiological information from the sensor can be transmitted at the same rate as achieved over the land-line or cellular communication systems.
The present invention establishes a communications hierarchy for the medical monitoring system. The medical monitoring system preferably has two basic communications paths between the remote monitoring unit and the central unit, the land-line telephone system and a wireless link such as the cellular-network system. Each of these communications paths has a relatively high communications bandwidth and can carry extensive data. However, in those cases where the basic communications system is unavailable, a third-network backup system, usually with a much narrower bandwidth, provides a minimal data set to define the event detected.